Field of the Invention and Related Art Statement
This invention relates to an endoscope device wherein the length of a signal cable for a solid state imaging device used in an imaging means of each electronscope is made equal to that of the other electronscope.
Recently, instead of an optical endoscope also called a fiberscope wherein an optical image formed by an objective in the tip part of an insertion part is transmitted to the holding side by an image guide formed of an optical fiber bundle, there has been used an electronic endoscope, also called an electronendoscope or electronscope, hereinafter, wherein an optical image formed by an object is photoelectrically converted to an electric signal by a solid state imaging device (referred to hereinafter as an SID of a charge coupled element referred to hereinafter as a. The electric signal or the like is transmitted to the holding side where the signal is fed to a video processor and the object image is displayed by a color monitor connected to the video processor.
In the above mentioned electronscope, the length of the insertion part for insertion inserted into a body cavity or pipe cavity is different depending on the uses. Therefore, the length of a signal cable inserted to the video processor, or a camera controlling unit, through the insertion part and a universal cord extended from the rear end side of the insertion part are also different.
When the length of the above mentioned signal cable is different, the resistance value of the entire signal cable is different. Therefore the output gain of the SID is different. The S/N fluctuates and the impedance of the cable end part is different. Therefore, in case the cable is connected at the end to the camera controlling unit, the waveform by the reflection is disturbed, the delay amount of the SID driving pulses from the camera controlling unit is different and the delay amount of the video output signal is different. Therefore, in the prior art example disclosed, for example, in U.S. Pat. No. 4,539,586, a matching circuit is built-in within a connector of each electronscope to regulate the output gain of the SID and the impedance to prevent the disturbance of the waveform.
In the above mentioned prior art example, there are defects in that a matching circuit is necessary for each electronscope and that the matching must be adjusted for each electronscope. Therefore, the number of component parts is large and the production cost is high. In the case of the products, it is difficult to keep the fluctuation of the characteristics within a fixed range and to provide products within a fixed standard.